Diatom response to climatic warming over the last 200Â years: A record from Gonghai Lake, North China

Annual monitoring data and centennial and millennial-scale paleolimnological records have revealed an increase in small-celled planktonic diatom species relative to heavier tycho-planktonic and small benthic diatoms in many high-altitude lakes, presumably in response to recent climatic warming. In addition to changes in the composition and structure of lacustrine diatom assemblages, there have also been changes in diatom biodiversity; however, these changes are not regionally consistent. In this study, we chose a temperate mid-latitude lake to explore the response of changes in diatom assemblages and biodiversity to recent climatic warming. The diatom record spans the past ca. 200 years and reveals that since 1966 CE the small-celled Cyclotella ocellata + stelligera has replaced the previously dominant, large-celled phytoplankton Cyclotella schroeteri. These changes are in accordance with the increasing trend in global mean surface temperature. Biodiversity increased remarkably from 1966 CE, but began to decline after 1990 CE, presumably in response to rapid climatic warming. Our findings indicate that the response of diatom biodiversity to climate change was a nonlinear process.